1. Field of the Invention
The present invention relates to fuse holders, and more particularly to in-line fuse holders adapted to accept miniature, relatively flat, plug-in fuses, such as those utilized in automobiles, which have a pair of flat terminals and a fuse link visibly retained within a relatively flat plastic case.
2. Description of the Prior Art
In general, it is desirable that a fuse be of the smallest physical size permitting required levels of current flow and yet assuring interruption of the flow of electrical current when required. Until recently, the most common type of fuses in the latter category were those having a sealed glass cylindrical envelope surrounding a fusible link electrically connected at opposite ends to terminal connectors capping each end of the glass envelope. This type of fuse has been used extensively in automobiles. Such a fuse, however, suffers the disadvantages of being bulky, fragile, somewhat difficult to handle, and having terminals exposed to undesired contact.
In an attempt to eliminate or overcome many of the drawbacks of the glass encapsulated type of fuse, a miniature plug-in fuse was developed which includes a pair of flat, terminals and a fuse link extending therebetween visibly retained within a transparent insulative plastic casing. The casing is relatively flat and the terminals are co-planar and protrude from one edge of the casing. Examples of this type of fuse are illustrated in U.S. Pat. No. 4,224,592-Urani & Gaia, assigned to the same assignee as the present invention, and those disclosed in U.S. Pat. No. 3,909,767-Williamson et al.
As the use of these miniature fuses has increased, the need for fuse holders which can accommodate them has similarly expanded. One of the most common types of fuse holders employed in the automotive industry and, in other industries as well, is the in-line fuse holder. Presently, the most common type of in-line fuse holder which accommodates miniature flat plug-in fuses includes a one-piece molded, soft plastic housing and single piece clip contacts for connection to the fuse terminals and to leads for external connection of the fuse holder. An example of such fuse holder is the Model 100, produced by Triplex Mfg. Company.
Construction of an in-line fuse holder with clip contacts of the aforementioned type limits material selection for such clip contacts to those materials having both good electrical conductivity to minimize resistive heating and good tensile strength to supply a tight electrical connection with the fuse terminals and to reduce contact resistance. However, even with the best material selection, compromises in both conductivity and tensile strength qualities must be made in order to achieve certain minimum qualities of both characteristics in one material. In addition, the use of soft plastic material to form the fuse holder housing provides little, if any assistance to the clip contacts in gripping the fuse terminals. The result is that because of the limited contact area of the terminals of the afore-mentioned miniature, plug-in fuses, the current carrying capacity of the fuse holder clips is restricted normally to 20 amps or less. However, the miniature plug-in fuses designed for use with these in-line fuse holders are available in current ratings as high as 30 amps. In addition, many modern automotive accessories and other products with low voltage power requirements also demand higher currents, often over 20 amps at these lower voltages.